Update:
I got a call from Mac's Radiator a few days ago. The high capacity 3-row core radiator came in last Thursday. My original plan was to put it in over the weekend, but it rained Friday, Saturday, and Sunday, so I wound up putting the new radiator in the Nova yesterday. I had to do a little modificatin on one mounting hole, but other than that, everything lined up, even though the new radiator is considerably wider and the old one. I put a FlowCooler high flow 160 degree thermostat in it, and got everything installed yesterday.
I fired up the engine and let it idle for about fifteen minutes. No leaks anywhere. After the engine warmed up, the temp got up to a little over 160, then dropped back when the thermostat opened. I watched it cycle a few times, and after about fifteen minutes, the engine temp went up to about 180 and stayed there. This morning I took the Nova out for a test drive, and the engine temp stayed right at 160, rock solid. So the overheating problem is fixed. Thanks to everybody for all the suggestions.
The next project is to get the exhaust system modified. When Kenny's Rod Shop had the exhaust system built, they had the pipes exit just in front of the rear wheel, which makes the exhaust noise way too loud inside the car, so I need to get the pipes lengthened so that the exhaust exits behind the rear wheel, not in front of it.
